The present invention relates generally to sensors and, more particularly, to a sensor having at least one photodetector that optically detects the location of an object within the field of the sensor.
Conventional optical or photoelectric sensors typically include a source of photons such as a light-emitting diode (LED); a collimating lens that collimates the photons emitted by the LED and that directs the photons toward a sensing field; a photodetector that detects the photons that have been reflected by an object within the field of the sensor; and a converging lens that directs the reflected photons (i.e., forms a convergent beam) toward an aperture of the photodetector. Generally speaking, these conventional convergent-beam-type photoelectric sensors provide a sensing output that is based on the absolute signal levels produced by the photodetector in response to photons which the photodetector receives from the near focal position of the sensor. Additionally, these conventional photoelectric sensors typically compare the absolute signal levels to a predetermined threshold value in order to determine whether an object is located within the field of the sensor. As a result, the sensing capability of these sensors is significantly affected by the surface conditions of the target (e.g., color, roughness, shape, etc.), background radiation or noise, and/or spurious reflections caused by objects not of interest but that are located within regions of the sensing field.
The present invention addresses one or more of these problems.
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention, and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
In accordance with one aspect of the invention, a sensor that optically detects a location of an object within a field includes first, second and third photodetectors arranged to receive photons from respective first, second and third sensing zones within the field. The sensor includes a processing circuit that receives first, second and third signals from the respective first, second and third photodetectors. One of the first, second and third signals is indicative of photons reflected by the object within the field and the processing circuit compares the one of the first, second and third signals to another one of the first, second and third signals in order to determine the location of the object within the field.
In accordance with another aspect of the invention, a sensor that optically detects the location of an object within a field includes a source of photonic radiation, a first lens, first, second and third photodetectors, a second lens, and a processing circuit. The first lens collimates photons emitted from the source of photonic radiation to form a collimated radiation beam that is directed into the field. The first, second and third photodetectors are arranged to receive photons from respective first, second and third sensing zones within the field; and the first, second and third sensing zones are adjacent to one another. The second lens directs photons reflected by the object within the first, second and third sensing zones to the respective first, second and third photodetectors. The processing circuit receives first, second and third signals from the respective first, second and third photodetectors and one of the first, second and third signals is indicative of photons reflected by the object within the field. The processing circuit compares the one of the first, second and third signals to another one of the first, second and third signals in order to determine the location of the object within the field.
In accordance with yet another aspect of the invention, a method of optically detecting a location of an object includes the steps of: emitting photons into a field; receiving photons reflected by an object within first, second and third sensing zones of the field; converting the photons to first, second and third signals corresponding to the first, second and third zones; and processing the first, second and third signals to determine the location of the object within the field.
The novel features of the present invention will become apparent to those of skill in the art upon examination of the following detailed description of the invention or can be learned by practice of the present invention. It should be understood, however, that the detailed description of the invention and the specific examples presented, while indicating certain embodiments of the present invention, are provided for illustration purposes only because various changes and modifications within the spirit and scope of the invention will become apparent to those of skill in the art from the detailed description of the invention and claims that follow.